Microsoft Defender

A Defender scan remaining at 91 percent does not identify the cause. Full scans can spend a long time on archives, disk images, or files that another program is actively changing. Restart Windows, install Windows updates, then open Virus & threat protection and check for protection updates. Run a Quick scan first. If it completes, use Custom scan on folders or drives to identify whether one location causes the stall, closing applications during each test. If you are concerned about malware, save your work and run Microsoft Defender Offline; it restarts into recovery and records the result in Protection history. You can update definitions from an elevated PowerShell window with Update-MpSignature. If Quick, custom, and offline scans all fail, note the elapsed time and affected path, check Protection history for an error, and report it through Feedback Hub. Repeated full scans without isolating the path will not identify the fault.